Fair Value Measurements - Schedule of Contingent Consideration Liabilities Measured at Fair Value (Detail) - Contingent Consideration [Member] - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 14,466	$ 14,864
Fair value adjustments	(149)	1,019
Settlements	(10,979)
Interest accretion	114	99
Foreign currency translation (gain) loss	(126)	180
Ending balance	$ 3,326	$ 16,162